Articles composed of materials having refractory characteristics, hardness and resistance to erosion have myriad important uses. Representative materials are described in U.S. Pat. No. 2,938,807 of Andersen.
Reaction sintering of .beta.-silicon carbide and .alpha.-silicon carbide has been known for making high temperature components. For example, .beta.-silicon carbide is described as an excellent binder in the Andersen U.S. Pat. No. 2,938,807, however, no diamond is incorporated in this silicon carbide technology.
Another useful component of these materials would be diamond. Its superior properties of, for example, hardness have long been appreciated. A satisfactory means of incorporating diamond into such articles would be of a significant advantage and such is an object of the process and product of the present invention.
A metal is used to bind diamond crystals in U.S. Pat. No. 4,063,909 to Robert D. Mitchell. Such metal may be, for example, Co, Fe, Ni, Pt, Ti, Cr, Ta and alloys containing one or more of these metals.
The above and other patents in the area of bonding diamond crystals depend on hot-press technology, as for example described in U.S. Pat. No. 4,124,401 to Lee et al, U.S. Pat. No. 4,167,399 to Lee et al, and U.S. Pat. No. 4,173,614 to Lee et al, all of which patents are assigned to the assignee of the present invention.
Many of these problems have been overcome by the invention disclosed in U.S. patent application Ser. No. 167,196, filed July 9, 1980 currently herewith by John Michio Ohno. The disclosure of this application is incorporated herein by reference.
In brief, that application describes bi-layer diamond composites having a special binder of .beta.-silicon carbide. That binder forms a matrix throughout the composite so as both to hold the diamond crystals and to unite the composite layers. The composites are formed by a process comprising:
(a) forming a first dispersion of diamond crystals and carbon black in paraffin;
(b) forming a second dispersion of carbon fiber, carbon black and filler in paraffin;
(c) compacting said dispersions together to produce an integral bi-layer composite;
(d) subjecting said composite to a vacuum for a period of time at a temperature sufficient to vaporize essentially all of said paraffin;
(e) liquefying said silicon to cause infiltration into both layers;
(f) uniting the layers of said composite with liquid silicon; and
(g) sintering the composite and infiltrated silicon under conditions sufficient to produce a .beta.-silicon carbide binder uniting said composite.
Notwithstanding that invention, however, various limitations on the construction of shaped diamond composite useful for these purposes remain. In particular, these involve placement of diamond crystals at desired surface locations.